Single-Cell Imaging Technology

This chapter will describe and assess the technology by which optical indicators are used to produce images that show the distribution of a measured quantity, such as free ion concentration or electric potential, within individual cells. Common ions whose free concentrations, or activities, can be imaged presently include Ca²⁺ , Mg²⁺ , Na⁺ , K⁺ , Cl^- , and H⁺ . In addition, many specific subcellular structures can be imaged by attaching fluorescent tags or antibodies. For studying intracellular messengers and their effects, the measurement of free ion concentrations is of prime importance and I shall concentrate on this, but an imaging experiment can often be usefully extended by using a fluorescent dye to image a subcellular compartment or structure, such as endoplasmic reticulum, from which the ionic signal may be thought to emanate.